Electrical metal tubing (EMT) is frequently employed as conduit for electrical wiring. The EMT is supplied in standard lengths, and, when being installed in an outdoor location, many connections typically must be made between the ends of the conduit and between the conduit and any electrical panels or electrical housings it is connected to.
Various connectors and fittings have been proposed to join two ends of conduit or tubing. Typically, the prior art proposes the use of an elastomeric seal, such as an O-ring to achieve a rain tight or liquid tight fit. U.S. Pat. No. 6,450,550 for example, discloses a fitting including an elastomeric seal that is mounted within the main cavity of the fitting. The inner diameter and outer diameter of the seal cause the seal to be compressed between the tubing and the wall of the main cavity.
U.S. Pat. No. 6,095,571 discloses a tubing connector for sealingly engaging an end portion of a tubing. An elastic seal ring is provided in each of two annular spaced apart grooves in an external periphery of a connector portion of the tubing connector. The elastic seal rings are preferably O-rings.
U.S. Pat. No. 4,310,185 discloses a quick connector that includes an O-ring seal positioned at each end of the sleeve and over each tubing end portion with an inner clamping sleeve, outer clamping sleeve, and locking sleeve.
U.S. Pat. No. 4,062,574 discloses a fitting assembly that includes a plurality of bores of increasing diameters in which a sealing ring in one bore is held in position by a retaining ring in another bore and a retainer member in the other bore holds the sealing ring and retaining ring in place.
Although all of the above prior art fittings claim to achieve a rain or liquid tight fit, they all rely upon the seal being created by one or more elastomeric O-rings held within the fitting. Typically the fitting includes one or more annular grooves machined within the inner cylindrical wall of the fitting to hold the elastomeric O-ring in place. Since the O-rings are elastomeric, they are elastic and function only to seal the outer periphery of the tubing against leaks. Being elastic, the O-rings do not function to hold the tubing in place within the fitting. Typically, the prior art fittings employ separate retainer rings or similar devices to hold the tubing in place within the fitting.
Prior art rain tight fittings for tubing, as a consequence of the reliance on one or more elastomeric O-rings and the machining required to form a groove for the O-rings, tend to be complex mechanically. Additionally, the elastomeric O-rings lose their elasticity with time. In the case of EMT, which is expected to be maintenance free for the life of the building, a fitting employing elastomeric O-rings would be unacceptable for service life. Another disadvantage of elastomeric O-rings is that they contribute nothing to gripping and holding the tubing within the fitting.
It is therefore an object of this invention to provide a mechanically simple fitting that is capable of obtaining a long-lasting rain tight fit on metal tubing. It is furthermore an object to create a sealing member that grips and retains the outer surface of the tubing to provide strain relief and prevent the tubing from being withdrawn from the fitting.